An organic photoreceptor containing an organic photoconductive material is most widely employed in the electrophotography. While the organic photoreceptor has such advantages that it is easy to develop materials corresponding to various exposing light source from visible to infrared light, materials without environmental contamination can be selected, and manufacturing cost is low, in comparison with the other photoreceptor, there is a problem that mechanical strength is weak and it is liable to generate deterioration or damage on a surface of the photoreceptor during a plenty sheets of copying or printing.
It has been strongly demanded to reduce an abrasion due to scraping by cleaning blade etc., so as to improve the durability of the organic photoreceptor. For this purpose technology to provide a protecting layer with high mechanical strength on the photoreceptor has been tried. For example, the patent document No. 1 reports that colloidal silica containing hardenable siloxane resin is used for the protective layer of the photoreceptor. The colloidal silica containing hardenable siloxane resin has high moisture absorbing characteristics both in hardenable resin having siloxane bond (Si—O—Si bond) and colloidal silica, and therefore, electric resistivity of the protective layer is liable to lower and causing image blur or image flow.
The other patent document No. 2 reports a protective layer composed of hardenable resin obtained by photo polymerizing a compound having acryloyl group etc., for the hardenable resin applied to the protective layer. Though fillers such as metal oxide are incorporated in the protective layer, bonding between the filler and the hardenable resin is weak, mechanical strength required to the protective layer is insufficient, and the problems of image blur or image flow is not dissolved sufficiently.
Patent document No. 3 discloses that trigonal α-alumina particles as a filler to incorporate in the protective layer are effective to improve an image blur. However, the bonding between the alumina particles and the hardenable resin is weak in the protective layer by this method, the alumina particles is not dispersed uniformly in the protective layer sufficiently, strength of the protective layer is not is insufficient, and cleaning deficiency is apt to occur.
Prior Art Reference
Patent document No. 1: JP-A H06-118681
Patent document No. 2: JP-A 2001-125297
Patent document No. 3: JP-A 2003-098712